1. Technical Field
The present invention relates to a method and apparatus for operating a computer network and in particular to a method of storing data in a distributed manner on such a network.
2. Related Art
The present inventor has recently described the benefits of storing computer data files in a distributed manner and has proposed a reliable data archival system based on this principle, in a paper entitled “Persistent, Reliable, Decentralised File System—DFS” published in the proceedings from the London Communications Symposium 2002, a copy of which is appended to this document as APPENDIX I. In this proposal, a data file to be stored in the distributed archive is firstly divided up into a plurality, k, of equally sized portions and then these are converted into a second larger plurality, n, of fragments by means of an “erasure code (k,n)” such that any k of the n fragments can be used to recover the original k portions and hence the complete data file.
The proposed data archive system is envisaged as working within a peer-to-peer or similar computer network in which computers may dynamically join and leave the network in an unpredictable manner. One requirement of the proposed scheme when operating in such a network is a discovery method for identifying which computers within the network are currently available for storing a new fragment of a data file to be archived. There are a number of discovery methods suitable for this purpose in use today, which use a variety of principles of operation; however, although these methods have various strengths which make them attractive for certain circumstances, there is still a requirement for an improved method for use in a large peer based network.